The present invention is directed to open-end spinning, and more particularly, to an improvement in the configuration of the navel assembly over which the yarn passes as it is lifted from the wall of the spinning chamber and delivered to the navel throat.
Open-end spinning is a fiber preparation technique which originated in Europe and has received wide-spread acceptance in the last 25-30 years. Open-end spinning is a distinctly faster operation than other yarn preparation techniques such as "ring" spinning; however, it has several limitations including a relatively high twist and a relatively low break strength. Also, open-end spinning techniques generally do not result in a yarn having a soft hand, because of the yarn structure itself, which includes an inner parallel sheath of fibers and outer non-parallel fibers and wrapper fibers. The non-parallel fibers impart a harsh hand to the yarn. In the case of knitted and woven apparel goods, a soft hand is often preferred. As a result, yarns intended for certain knitted and woven apparel fabrics have not achieved wide-spread acceptance from open-end spinning systems.
For these and other reasons, it has been previously attempted to obtain a softer hand, and eliminate ends down situations by introducing one or more obstacles in the path of the yarn after it leaves the wall of the spinning rotor and enters the throat of the delivery tube. At such times, the spinning rotor causes the yarn to rotate around the inner periphery of the outlet or delivery tube as it passes therethrough engaging such obstacles as it rotates. This results in some surface treatment of the yarn. Such approaches are illustrated in U.S. Pat. Nos. 4,258,541 to Le Chatelier et al.; 4,011,712 to Egbers et al.; and 4,516,397 to Raasch et al. Another approach which introduces a plurality of elongated ceramic rods in the inside wall of the delivery tube is illustrated and described in U.S. Pat. No. 4,712,369 to Vernon. Other approaches have provided one or more spiral obstacles or on the surface of the navel to provide a twist blocking element. These approaches are illustrated in the U.S. Pat. Nos. 4,702,069 to Maximov et al. and 4,665,687 to Ott et al.
While such approaches have achieved a certain level of success, other areas for improvement have remained unaddressed. First of all, the distance between the point at which the yarn first engages the navel or take-up device which creates false twist and the point at which the yarn is lifted from the wall of the spinning chamber (known as the "twist zone") has been relatively long, which has been a deterrent in achieving higher speeds. Long twist zones require a higher twist to successfully peel the yarn off the wall of the spinning chamber. The higher twist is not conducive to a softer hand. Further, the longer twist zone has been a hindrance to improved yarn evenness, imperfection levels, and break strength.
With these limitations in mind, the present invention is an attempt to provide a superior yarn at increased production levels by shortening the aforedescribed twist forming zone. In general, the twist forming zone is shortened by introducing a circular ridge or projection in or adjacent to the surface of the navel member at or adjacent the periphery thereof. In one approach, one or more circular ridges are attached to the peripheral rim of the navel support member. In a second approach, the projection is a separate outer ring which includes an annular rim that extends above the surface of the navel member. By the introduction of such ridges or projections, the twist forming zone is shortened considerably (on the order of 10-30%). The navel member, as used herein, is defined as the ceramic or stainless steel member generally supported by a support housing or navel body mounted in the rotor faceplate. The yarn initially passes over the navel member as it leaves the yarn collection surface or wall of the rotor on its way to the yarn delivery tube and/or take-up mechanism.
In general then, the present invention is directed to an improved navel member or assembly for open-end spinning devices of the type having a driven spinning chamber with the navel mounted coaxially therein and having a curvilinear inner surface. The navel assembly is improved by providing at least one circular projection on or adjacent the surface of the navel itself which projection extends upwardly from the surface thereof. The circular projection(s) has a height of at least 0.003" and is located in such proximity to the edge of the navel that the yarn being formed and lifted from the wall of the spinning chamber first engages the aforesaid projection, rather than the surface of the navel member. This then assists the false twist in reaching the wall of the spinning chamber.
More specific parameters to be considered are the variations in height of the impediment or ridge, the material from which the ridge is formed, the placement of the ridge, and the like which have been considered and are described hereinbelow. However, the primary or central feature of the invention is the existence of the circular ridge placed concentrically about the longitudinal axis of the delivery tube at or adjacent to the periphery of the navel member.
It has been found that navel members formed in accordance with the present invention result in improved rotor speeds on the order of 8-10%; increased production on the order of 20% in the case of polyester/cotton blends; a decrease in the twist multiple utilized; improved evenness; improved imperfection levels; and improved break strength. Also, the shortened twist forming zone which provides for the lower twist results in a softer or better hand in the yarn and requires less twist to peel the yarn off the wall of the spinning chamber in the yarn formation zone. The resulting yarn has less shedding and less outer wrapper fibers.
It is therefore an object of the present invention to provide a unique and improved construction for the navel assembly of open-end spinning frames.
It is another object of the present invention to provide a navel member of the type described which results in a softer hand and a higher quality thread output.
Another object of the present invention is to provide a navel member of the type described which provides for higher processing speeds without attendant problems.